"UDS is over! And in the customary wrap-up I stood up and told the audience what the Foundations team have been discussing all week. One of the items is almost certainly going to get a little bit of publicity. We are going to be doing the work to have btrfs as an installation option, and we have not ruled out making it the default. I do stress the emphasis of that statement, a number of things would have to be true for us to take that decision."

Yeah right.
When did Ubuntu start using Grub 2?
When did Fedora start using Grub 2?
F12 certainly does not.
From a recent LUG problem report, it appears that 9.10 does and it appears that quote a lot of people are really having fun (not) with it.

IMHO (Which might be wrong) it seems that Canonical are a little more 'gun-ho' with stuff that is not quite ready for 'prime time' so to speak than Fedora. Given the higher usage of Ubuntu, I'm not convinced that this is all together a good thing.

I'm hoping the F13 is pretty stable as my guess is that a lot of it will be used in RHEL 6 later this year.
Just my 2p worth on the subject.